Select by Mass — BIMO Documentation

Select by Mass uses selected Revit Masses as spatial filters and selects instances from configured categories whose geometry intersects their volume. For rooms and other spatial elements, it checks the element location point. The result can also be limited to elements visible in the active view.

The command is located on the BIMO tab, in the Select panel, under Select by Mass.

Important: the command only changes the current Revit selection. It does not modify element parameters or geometry and does not start Temporary Hide/Isolate. The result replaces the previous selection.

When To Use It

Select rooms assigned to a building section represented by a Mass.
Find walls, doors, equipment, or other categories in a volumetric zone.
Prepare elements for bulk parameter editing.
Narrow a large project to elements associated with one or more Masses.
Select only matching elements that are visible in the current view.

Before You Run

Open a Revit project document. Family documents are not supported.
Prepare one or more elements in the Mass category with valid solid geometry and positive volume.
Check the position and dimensions of the Masses in the model.
Choose the result categories in the command settings.
If using Only visible on view, open the required view first.

The command works with the current host document only. Elements inside linked Revit models are not processed.

Command Settings

Setting	What It Does
`Categories`	Required list of categories to search. The default is `Rooms`. At least one category must be selected.
`Only visible on view`	After the spatial search, keeps only elements that the Revit API reports as visible in the active view. It is off by default.

Category names are validated against the current document. If a preset was created in another Revit language and a category is reported as invalid, select it again from the current project settings.

How To Use It

With Preselected Masses

Select one or more Masses in Revit.
Run BIMO > Select > Select by Mass.
Review Categories and Only visible on view in the settings window.
Confirm the command.

If the current selection contains at least one valid Mass, BIMO uses every selected Mass and does not open an additional picking mode. Other preselected elements are ignored.

Without A Preselection

Run Select by Mass.
Confirm the settings.
Pick one or more Masses in Revit. Elements from other categories cannot be picked.
Finish the standard Revit multi-selection.

After processing, BIMO replaces the current selection with the matching elements.

How The Result Is Determined

For each selected Mass, the command extracts every solid with positive volume and searches element instances only in the configured categories.

Regular Elements

For walls, doors, equipment, and other non-spatial elements, the command tests geometric intersection with the Mass solid.

Important: an element does not need to be completely inside the Mass. If its geometry crosses the volume boundary, it can also be included.

Rooms And Other Spatial Elements

For SpatialElement instances, including Rooms and Spaces, the command checks the location point. An element is included when that point is inside the Mass solid.

The room boundary is not compared with the Mass boundary. A room that crosses a section boundary is therefore assigned to the Mass containing its location point.

Multiple Masses

When several Masses are selected, their results are combined. An element only needs to match one solid from one selected Mass.

Only Visible On View

When Only visible on view is enabled, the Revit visibility filter for the active view is applied after the intersection search. The geometry search still runs in the host document, and results not visible in the active view are then removed.

Examples

Assign Section Numbers To Rooms

Create a Mass for each building section.
Keep Rooms in Categories.
Select the Mass for the required section and run the command.
Review the selected rooms.
Fill the section-number parameter with standard Revit tools or another verified command.

Remember that Room membership is determined by its location point.

Select Several Categories In A Volume

Add categories such as Walls, Doors, and Mechanical Equipment. Select the zone Mass and run the command. Elements whose geometry intersects the Mass solid are combined into one selection.

Limit The Result To The Active View

Open the required plan or 3D view, turn on Only visible on view, and perform the selection. Elements that the Revit API does not report as visible in that view are excluded.

Presets, Variants, And Keyboard Shortcuts

Select by Mass supports presets. Each preset stores:

the Categories list;
the Only visible on view state.

Frequently used presets can be assigned to Variant #1, Variant #2, and Variant #3. A variant with valid settings runs without reopening the settings window, then uses preselected Masses or asks you to pick them.

Before a quick launch, verify the active document, view, selected Masses, and preset categories.

For setup details, see Presets and Variants.

Errors And Troubleshooting

Problem	What To Check
The command does not run in a family	Open a Revit project document.
The required object cannot be picked	The command accepts only a `FamilyInstance` in the Mass category. Generic Models and other categories are not accepted.
A solid-retrieval error appears	Confirm that the Mass exposes solid geometry with positive volume. Empty or void-only forms are not supported.
Nothing is selected	Check the Mass intersection, category list, and Only visible on view setting.
A boundary-crossing element is unexpectedly selected	Regular elements use intersection, not complete containment.
A room is associated with another Mass	Check the room location point. Its boundary is not used for this test.
A category is reported as invalid	Select the category again from the current project, especially after changing the Revit language.
Linked-model elements are missing	The command does not search linked documents. Run it inside the relevant model.
Some results disappear	Check the active view and Only visible on view state.
A complex or transformed Mass gives unexpected results	Verify its solid geometry on a test set; the current implementation extracts instance geometry through the Revit family geometry API.

Known Limitations

Works only in project documents.
Uses Masses from the current host document and does not process linked models.
Selects element instances, not element types.
Tests intersection for regular elements, not complete containment.
Uses the location point for spatial elements, not room or space boundaries.
A Mass must provide at least one solid with positive volume.
Complex, nested, or transformed family geometry should be verified on a test set.
Always replaces the current selection; Add, Remove, and Intersect modes are not available.
Does not display a final report or result count.
Processing several complex Masses and broad category lists can take time.